breathing apparatus vs breathing device

breathing apparatus and breathing device both are nouns.

Word	Noun	Adjective	Verb	Adverb
breathing apparatus	Yes	No	No	No
breathing device	Yes	No	No	No

As nouns, breathing apparatus and breathing device are synonyms defined as:

breathing apparatus and breathing device: a device that facilitates breathing in cases of respiratory failure

Other synonyms of breathing apparatus include breathing machine, ventilator.

breathing apparatus (noun)	breathing device (noun)
a device that facilitates breathing in cases of respiratory failure	a device that facilitates breathing in cases of respiratory failure